The invention relates to a composition of polyanhydroglucuronic acid (PAGA) and its salts. The term polyanhydroglucuronic acid and salts thereof as used herein includes copolymers thereof, especially with anhydroglucose.
1. Field of the Invention
Wounds occurring in human and veterinary practice often involve minor lesions such as cuts, excoriations, bums, scalds, and various kinds of open efflorescences be it of eczematous or bacterial origin. Such lesions require rapid covering to arrest bleeding, to disinfect the wound area, and to suppress secondary microbial contamination.
It is widely accepted that the healing essentially consists of three stages which may be simply defined, as: inflammatory/exsudative phase (Phase 1), proliferative phase (Phase 2), differentiation phase (Phase 3).
It is especially important for the healing process to arrest bleeding and to suppress secondary microbial contamination of the wound. Through infiltration of the, exsudate, the wound is supplied with leucocytes, neutrophilic granulocytes and monocytes, subsequently being converted to macrophages. Insufficient treatment of even minor lesions may thus give way to massive infections and to considerable complications of the healing process.
2. Description of the Related Art
The hemostatic effect of oxidised cellulose, introduced into health care practice by pioneering work of Kenyon, Nevell, Rogovin, Jasnitzky and others, has been known since the 1940""s. Mechanisms underlying the hemostatic activity of PAGA have been recently explicitly reported e.g. by V A Stelmah et al. (Vestn. Beloruss. Gos. Univ., Ser. 2 (1993), (2) 43-5; cf. CA 1994:570118) to consist in an acceleration of formation of thrombi. The oxidised cellulose is prevailingly manufactured in the form of woven or knitted tissue (such as Surgicel or Interceed by Johnson and Johnson, USA). Its application is therefore mostly limited to specialised institutions such as surgical clinics or ambulances. Also, the existing products have certain contraindications due to their relatively high acidic character. Another disadvantage of the existing products is due to the fact that opening of the sterile packaging outside a sterile area may bring about bacterial contamination of both the sterile product and the wound; the same problem of course applies even to powder form packaged and sterilised in e.g. plastic bottles.
A detailed discussion regarding polyanhydroglucuronic acid and salts thereof is included in our co-pending Patent Application having the same date of filing as this application.
Pressurised aerosol packagings have been available from the 1930""s, originally as insect sprays also used during World War II, using chlorofluoroalkanes as the propellant gas. They have been applied to pharmaceutical products since the 1950""s, and there has been considerable development towards other types of propellantsxe2x80x94less depleting the ozone layer and less contributing to global warmingxe2x80x94in the last decades. However, there is no awareness of an aerosol packaged hemostatic of the polyanhydroglucuronic acid type prepared on the basis of oxidised cellulose as yet.
It is therefore the aim of the present invention to provide a product based on polyanhydroglucuronic acid and its salts for use as a sterile absorbable local hemostatic for mass usage by both layman and professional public, enabling easy and rapid application in common wounds and lesions and minimising detrimental effects on the environment.
According to the invention, there is provided a hemostatically active aerosol composition comprising from 0.005 to 0.25 weight parts of microdispersed/microdispersable polyanhydroglucuronic acid and/or salts thereof and from 0.75 to 0.995 weight parts of a suitable dispergating/propellant system wherein the dispergating/propellant system includes liquids which are non-polar or of low polarity and have a surface tension of less than 30 mN/M and a permitivity at 10 kilohertz of less than 10. The term polyanhydroglucuronic acid and salts thereof includes copolymers thereof, especially with anhydroglucose.
The hemostatically active aerosol composition of the invention enables easy and rapid administration and ensures permanent readiness for use, sterility at repeated application, and increased stability due to exclusion of air and UV light access to the product in a pressurised aerosol packaging.
The composition may include at least one pharmaceutical adjuvant which may be selected from one or more substances having suitable anti-microbial, anti-viral, anti-mycotic and/or anti-parasitic effects.
In one embodiment of the invention, the stable microdispersed polyanhydroglucuronic acid and/or salts thereof have the form of particles of 0.1 to 80 xcexcm preferably 5 to 15 xcexcm, in size.
In one embodiment of the invention, the propellant used comprises aliphatic and/or alicyclic hydrocarbons with a number of carbon atoms from 1 to 6 and/or aliphatic ethers and/or fluorinated and/or perfluorinated aliphatic hydrocarbons and/or ethers, and/or carbon dioxide and/or nitrogen and/or rare gases and, as the case may be, other auxiliary substances.
The polyanhydroglucuronic acid salts are preferably selected from calcium, magnesium, sodium and/or potassium salts.
The polyanhydroglucuronic acid and/or salts thereof are preferably prepared by a method wherein a polyanhydroglucuronic acid-containing material is subjected to partial or complete hydrolysis and neutralisation in an oxidative environment, the hydrolysate undergoing fractional coagulation to form a stable microdispersed product.
This method provides stable polyanhydroglucuronic acid and salts thereof in essentially a single process carried out in a single vessel.
Preferably the hydrolysis is carried out in an aqueous solution of inorganic and/or organic salts and/or bases. Most preferably the inorganic and/or organic salts and/or bases used for hydrolysis are chlorides, sulphates, carbonates, formates, or acetates of alkali and/or alkaline earth metals, hydroxides of alkali and/or alkaline earth metals, alkylamines, or alkanolamines, in concentrations ranging from 1 to 10xe2x88x923 to 5 mol/l.
In an especially preferred embodiment of the invention the oxidative environment during hydrolysis is established by the presence of agents selected from one or more of hydrogen, sodium or magnesium peroxide, peroxacides and their salts, hypochlorites and chlorites.
Preferably the procedure is carried out at a pH of from 1 to 12, and preferably, at a temperature of from 0 to 100xc2x0 C.
In a preferred embodiment of the invention the polyanhydroglucuronic acid-containing material is obtained by oxidation of a suitable polysaccharide, such as native or regenerated cellulose or starch.
The polyanhydroglucuronic acid and salts thereof preferably contain in their polymeric chain from 8 to 30 percent by weight of carboxyl groups, at least 80 percent by weight of these groups being of the uronic type, at most 5 per cent by weight of carbonyl groups, and at most 0.5 percent by weight of bound nitrogen.
Preferably the product contains at most 0.2 percent by weight of bound nitrogen in the polymeric chain.
In a preferred embodiment of the invention the molecular mass of the polymeric chain is from 1xc3x97103 to 3xc3x97103) Daltons most preferably from 5xc3x97103 to 1.5xc3x97103 Daltons.
The content of the carboxyl groups is in the range of from 12 to 26 percent by weight and at least 95 percent of these groups are of the uronic type.
In a particularly preferred embodiment of the invention the product contains at most 1 percent by weight of carbonyl groups. Typically the carbonyl groups are intra- and intermolecular 2,6 and 3,6 hemiacetals, 2,4-hemialdals and C2-C3 aldehydes.
Because neutralisation and refining is carried out in a single operation the process is cost effective.
As the product is in a microdispersed form there is enhanced sorption and greater accessibility for blood. Therefore the biological availability is increased and a rapid onset of hemostatis. We have also observed that the product also assists wound healing as a large surface area is presented which is quickly penetrated by body fluids and goes into solution in these fluids. We believe that the product then chemically degrades to achieve more rapid absorption and enhancement of the wound healing process.
The overall homogeneity of the distribution of oxidised groups within the product is increased. Thus, the product has improved reactivity and accessibility to reactive sites for the purpose of binding ocher substances such as pharmacologically acnve substances to the product. The average degree of polymerisation is decreased, the distribution of the polymerisation is narrowed and the amount of cellulosic fractions are reduced. This also assists in biodegradation.
The polyanhydroglucuronic acid and salts thereof may be made up of particles sized from 0.1 to 100 xcexcm and/or fibres of from 5 to 30 xcexcm diameter and up to 30 mm length.
Preferably the hydrolysate is let to undergo fractional coagulation by a suitable water-miscible organic solvent, the coagulated product is washed, or dehydrated, using a suitable water-miscible organic solvent, and/or converted, in an appropriate manner, for intended subsequent use.
Preferably the inorganic and/or organic salts and/or bases preferably used for hydrolysis are chlorides, sulphates, carbonates, formates, or acetates or alkali and/or alkaline earth metals, hydroxides of alkali and/or alkaline earth metals, alkylamines, or alkanolamines, in concentrations ranging from 1xc3x9710xe2x88x923 to 5 mol/l.
Preferably the oxidative environment during hydrolysis is established by the presence of oxidative agents such as hydrogen, sodium or magnesium peroxide, peroxacides and their salts, hypochlorites, or chlorites.
The invention will be more clearly understood from the following description thereof given by way of example only.
The essence of the invention consists in the ability of the microdispersed polyanhydroglucuronic acid and salts thereof to form stable dispersions in physiologically indifferent liquids displaying low to zero rate of sedimentation low viscosity of these colloid-dispersion non-aqueous systems and no tendency to agglomerate at concentrations of 0.5 to 15% b/w.
Of important advantage is the fact that the physicochemical properties of the microdispersed polyanhydroglucuronic acid can be controlled to fit the dispergating liquid or mixture of liquids, thus allowing stable systems suitable as spray fillings to be prepared.
Extensive tests have shown that the microdispersed polyanhydroglucuronic acid and salts thereof prepared by controlled hydrolysis and fractionation, mostly in the form of particles smaller than the size of an erythrocyte, is capable of stimulating the activity of histiocytes and macrophages, which represents another essential advantage of the application of such substances. At the same time, they effectively arrest capillary bleeding of the wound area while getting incorporated into the fibrin net formed. Due to small size of the order of microns, the particles of the microdispersed polyanhydroglucuronic acid and salts thereof undergo, dependent on the chemical composition and physiochemical properties, relatively rapid enzymatic hydrolysis in the wound environment yielding glucose and glucuronic acid, substances inherent to living organism, as final products; in fact, histological observations indicate that they are presumably incorporated into body mucopolysaccharides. Close to neutral pH value of extracts of salts of microdispersed polyanhydroglucuronic acid also substantially contributes to their biocompatibility; no adverse secondary effects due to acidic nature have been reported in their applications.
The presence of reactive carboxyl groups in the microdispersed polyanhydroglucuronic acid and salts thereof is the basis for their ability to chemically bind substances with antibacterial effects such as e.g. derivatives of biguanid, quaternary ammonium salts, or aminosaccharide based antibiotics. Bactericidal activity is also observed for salts or complex salts of certain cations, such as Zn2xe2x88x92, Cu2xe2x88x92, and to a limited extent Ag+, with microdispersed polyanhydroglucuronic acid.
Similarly, we have observed that preparations based on the microdispersed polyanhydroglucuronic acid and salts thereof display certain insecticidal activity, This activity can be enhanced using hydrophobic reactivity of polyanhydroglucuronic acid molecules which allows to anchor on the powder substance non-toxic synthetic derivatives of natural pyrethrins such as pyrethroids, notably Permethrin (cis/trans isomer ratio 1:3). Another advantage of compositions according to the invention is thus represented by the possibility to combine in a single product, hemostatic, bacteriostatic, and insecticidal function. This is important in veterinary medicine for the treatment of both traumatic and artificial lesions in e.g. sheep and cattle, in that it provides a temporary protection against microbial infection and insect attack during healing.
An example of successful combination of an antibiotic and a hemostatic may be represented by the application of neomycine ut sulfas and bacitracinum zincicum of bound to a sodium/calcium salt of microdispersed polyanhydroglucuronic acid.
The main problem that had to be solved within the invention concerns the choice of dispergating liquids and propellants to be used in aerosol packaging formulations of the microdispersed polyanhydroglucuronic acid and salts thereof.
Extensive tests have surprisingly revealed that the use of organosols containing several different substituents or highly polar substituents caused the system to easily form coacervates or even to coagulate.
We have found that eg alcoholic dispersions display a relatively low stability with a rapid coagulation and/or sedimentation of particles. The stability is increased with increasing size of the aliphatic chain of the molecule but the application of higher alcohols is limited from the physiological point of view. We have also found that the hemostatic efficacy of the microdispersed polyanhydroglucuronic acid based products in the initial phase immediately after the spray administration is reduced by the presence of water or polyhydroxycompounds such as glycerol and its derivatives, glycols and polyglycols. Univalent alcohols such as ethanol can induce a stinging pain on application to the wound. Substances of the latter types are therefore preferably avoided in the formulation.
Coagulation and/or sedimentation was surprisingly equally observed in systems where a substance with low polarity has been used, but the molecule contained several different substituents giving rise to an electrostatic non-equilibrium, the examples of these being dichlorotetrafluoroethane or trichlorofluoromethane. In contrast low polar substances such as alkanes, C1 to C8 cycloalkanes, or their fluorinated and perfluorinated derivatives, yielded stable dispersion systems with a low sedimentation rate. Examples are methane, ethane, propane, butane, isobutane, pentane, 2-methylbutane, 2-methylpropane, 2,2-dimethylpropane and the like. Substances with 3 to 5 carbon atoms such as pentane, neopentane, or a pure petrol fraction free from mercaptanes and aromatics may preferably be used to reduce loss at administration, to improve fixation of the substance upon the treated area.
We have further found that the organic liquid molecule may also contain a heteroatom, preferably oxygen, in the main chain without deteriorating the system stability. Such substances would involve ethers such as dimethylether, diethylether, but also perfluorinated ethers of the methoxy- or ethoxy-nonafluorobutane type.
Extensive tests have shown that the product, though involving an important number of hydrophilic polar groups, can best be dispergated in low polar or non-polar liquids with a low surface tension and low relative permitivity. In contrast, we have found that liquids with higher polarity and higher surface tension tend to support agglomeration of the product particles and thus to jeopardies the correct function of the aerosol packaging. Besides the effect of microparticles with a large specific surface area the good dispersability of the microdispersed polyanhydroglucuronic acid and salts thereof may be attributed to their ability to enter, in spite of the presence of hydrophilic groups, hydrophobic interactions with the dispergating liquids. The results indicate that stable dispersion systems can preferably be obtained using those of the above substances which display a value of the relative permitivity (dielectric constant at 25xc2x0 C. and 10 kHz) less than 10, preferably less than 5, and that of the surface tension less than 30 mN/m, preferably less than 18 mN/m. Thus the substances recommended for use involve, preferably, C3 to C5 alkanes, isoalkanes, or cycloalkanes, 1,1,1,2-tetrafluoroethane, dimethylether, methoxy- and ethoxy-nonafluorobutane and mixtures thereof.
Besides the ability to form low sedimenting dispersion systems, the overall criteria limiting the choice of suitable dispergator/propellant systems further include: physiological indifference (low toxicity, zero or minimum skin and cardiac sensitisation at exposures up to 100000 ppm, no mutagenicity and carcinogenicity, minimum solubility in water and body fluids), indifference in contact with the active substance, high volatility and low heat of evaporation, ability to fix the active substance in the first phase immediately after application on the wound surface, environmental acceptability, and cost.
It is difficult to draw a sharp demarcation line between the dispergating medium suitable for the microdispersed polyanhydroglucuronic acid and salts thereof and the propellant since in some cases both functions can be provided for by one and the same substance such as e.g. n-butane or isobutane. In general, the relevant substances may especially involve:
a) Aliphatic and alicyclic hydrocarbons with 1 to 6 carbon atoms, or aliphatic ethers, notably dimethylether, diethylether, and diisopropylether. While aliphatic hydrocarbons with 1 to 3 carbon atoms could well serve as dispergators for the microdispersed polyanhydroglucuronic acid and salts thereof when under pressure, they evaporate immediately at the output of the spray outlet and thus increase the powder dissipation on spraying and insufficiently fix the powder on the wound surface. It is therefore preferable to use higher hydrocarbons such as n-butane, isobutane, n-pentane, or isopentane for the given purpose. This group may also include petrolether, pentane/isopentane fraction from petroleum distillation, or a mixture of liquid hydrocarbons currently distributed under the name of medicinal petrol, under the obvious condition of being pure enough from aromatic hydrocarbons and mercaptanes. From the ether group, dimethylether can preferably be used with respect to its suitable physicochemical characteristics.
b) Nonflammable compounds known as fluorohydrocarbons (HFC), perfluorocarbons (PFC), and recently introduced hydrofluoroethers (HFE). Compared to chlorofluorocarbons (CFC), the HFC""s, PFC""s and HFE""s display much reduced life time in the atmosphere and zero to very low ozone-depleting potential (ODP) and global warming potential (GWP). Some may have a slightly increased toxicity and bioreactivity; however, their contact with the wound is very short due to the rapid evaporation rate. The most suitable choice with respect to the properties may be represented by 1,1,1,2-tetrafluoroethane (HFC 134a) or hydrofluoro-ethers such as methoxy-nonafluoroethane (HFE 7100) or 1,1,1,2,3,3-hexafluoro-3-methoxypropane, all of these substances being acceptable from both the physiological and environmental point of view.
Representatives of both above groups are liquids or substances liquefiable at low pressures (0.2-1.4 Mpa) at normal conditions. Further alternatives include:
c) Gaseous substances, which cannot be liquefied at normal conditions, but capable of being absorbed, at least partially in the powder active substance or in the liquid dispersion system. These include notably carbon dioxide and nitrous oxide.
d) Gaseous substances not liquefiable at normal conditions and displaying a very limited absorption ability in the liquid dispersion system, such as rare gases, air and nitrogen.
All of these substances can further be suitably combined with each other to provide for an optimized function of the spray. Based on extensive testing, the preferred combinations include systems such as n-butane or n-pentane/CO2, medicinal petrol/HFC 134a, isopentane/dimethylether, medicinal petrol/HFE 7100/HFC134a, HFE 7100/CO2, n-pentane/HFE 7100/N2.
In summary, the important fact underlying the present invention is that the polyanhydroglucuronic acid and salts thereof create stable dispersion concentrates in liquids that do not compromise the environment, displaying zero or low values of both the ODP and GWP potentials.
An important advantage of the aerosol packaged hemostatic according to the invention consists in the fact that the contents of the packaging can repeatedly be used without the loss of their sterility. The dosing of the active substance can accurately be directed to the wound surface where the powder gets well anchored due to the relatively high speed of incidence of an indifferent dispersion in a liquid that is immiscible with the body fluids and evaporates within a few seconds.
Certain adverse secondary effects are reported for the above listed dispergating and propellant substances, such as weak narcotic effects or skin degreasing on contact for C5 hydrocarbons. However, no such effects have been observed during extensive application tests of the sprays according to the invention because of small applied amounts and short contact time.
An additional specific advantage can be attained when using substances listed under a) above or combinations of substances listed under a) and c) above for preparing the stable dispersions of the microdispersed polyanhydroglucuronic acid and salts thereof. Such formulations of the spray allow a simple terminal sterilisation of the finished aerosol packagings to be preformed by gamma radiation.